This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Glutathione transferases (GST) are detoxification enzymes that inactivate reactive hydrophobic compounds by conjugating the tripeptide glutathione to reactive centers on these compounds. We have been using NMR spectroscopy to characterize the dynamic properties of one human isoform, GST A1-1. We have shown that the carboxy-terminal alpha helix becomes docked when either substrate or product bind to the enzyme. Currently we are generating mutations in the protein that may be responsible for stabilizing the docked form of this helix and investigating the enzymatic and dynamic properties of these enzymes. To complement the NMR studies, we would like to investigate the effects of these mutations on the dynamics of the protein using molecular mechanics calculations. We feel that the molecular mechanics calculations will aid in the interpretation of our laboratory date and may provide a means to predict the outcome of future experiments. The protein is a homo-dimer of 50,000 kDa overall molecular weight. We would like to perform dynamics calculations on the wild-type enzyme and three mutants (Ile219Ala, Phe220Ala, Phe222Ala, for both the unliganded and the enzyme-product complex. The crystal structure of the enzyme-product complex will be used for starting coordinates. We intend to employ CHARMM using a solvated system with periodic boundary conditions. We will initially perform dynamics runs for ~5ns to gauge whether there are significant difference between the eight different forms of the protein (apo + liganded/wildtype + 3 mutants). We anticipate equilibration of the system in-house on our sgi origin 300 server. Please allocate the appropriate number of service units.